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A Infertilidade e função tiroideia: a sua relação e respetiva abordagem terapêutica
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Abstract(s)
Segundo a Organização Mundial de Saúde, a infertilidade é uma “doença do sistema
reprodutor masculino ou feminino definida pela incapacidade de conseguir uma
gravidez após 12 meses ou mais de relações sexuais regulares desprotegidas”.
Atualmente, estima-se que existam 186 milhões de casos e a sua prevalência crescente,
torna premente o estudo da sua etiologia.
As disfunções tiroideias são uma das possíveis causas de infertilidade, sendo esta
relação o objeto de estudo da presente dissertação. Sendo que as hormonas tiroideias
interagem diretamente com recetores presentes nos órgãos reprodutores e interferem
com o eixo hipotálamo-hipófise-gonadal, podem conduzir a distúrbios menstruais e
ovulatórios e alterar o padrão de secreção de outras hormonas importantes para a
foliculogénese, desenvolvimento do endométrio e implantação do embrião. Nos
homens, estas disfunções comprometem a espermatogénese e a síntese de
testosterona, bem como a motilidade dos gâmetas, capacidade ejaculatória e o
desenvolvimento testicular.
Perante as evidências apresentadas, foram estabelecidas recomendações quanto à
abordagem a adotar que incluem a suplementação oral com levotiroxina, em estados
hipotiroideus, sobretudo se detetada a presença de anticorpos antitiroideus, e o uso de
fármacos antitiroideus, tratamento com iodo radioativo ou cirurgia, em estados
hipertiroideus, sendo o objetivo destas intervenções, atingir um estado eutiroidiano
estável. Quando esta abordagem não é suficiente para se concretizar uma gravidez,
poderá recorrer-se a técnicas de procriação medicamente assistida, como a fertilização
in vitro e a injeção intracitoplasmática de espermatozoides. Na gravidez, recomenda-se
o início do tratamento com levotiroxina ou o aumento da sua dose, quando os níveis da
hormona estimuladora da tiroide estão muito elevados. Em contrapartida, níveis baixos
não são preocupantes e a toma de fármacos antitiroideus deve ser evitada.
Atualmente, o estabelecimento destas recomendações e o aparecimento de novas
tecnologias tem contribuído para potenciar a fertilidade dos casais e concretizar o
desejo que muitos têm de serem pais.
According to the World Health Organization, infertility is a “disease of the male or female reproductive system defined by the inability to achieve pregnancy after 12 months or more of regular unprotected sexual intercourse”. Currently, there are an estimated 186 million cases and its increasing prevalence makes it urgent to study its etiology. Thyroid dysfunctions are one of the possible causes of infertility, and this relationship is the object of study of this dissertation. Since thyroid hormones interact directly with receptors present in the reproductive organs and interfere with the hypothalamic-pituitary-gonadal axis, they may lead to menstrual and ovulatory disorders and change the secretion pattern of other hormones important for folliculogenesis, endometrial development and embryo implantation. In men, they compromise spermatogenesis and testosterone synthesis and have effects on gamete motility, ejaculatory capacity and testicular development. Regarding the evidence presented, recommendations have been established as to the approach to be adopted, which include oral levothyroxine supplementation in hypothyroid states, especially if the presence of antithyroid antibodies is detected, and the use of antithyroid drugs, treatment with radioactive iodine or surgery, in hyperthyroid states, being the aim of these interventions to achieve a stable euthyroid state. When this approach is not sufficient to achieve pregnancy, medically assisted procreation techniques such as in vitro fertilization and intracytoplasmic sperm injection may be used. In pregnancy, it is recommended to start levothyroxine treatment or to increase the dose, when thyroid stimulating hormone levels are very high. Conversely, low levels are of no concern and the taking of antithyroid drugs should be avoided. Currently, the establishment of these recommendations and the emergence of new technologies have contributed to boost the fertility of couples and fulfil the desire that many have of becoming parents.
According to the World Health Organization, infertility is a “disease of the male or female reproductive system defined by the inability to achieve pregnancy after 12 months or more of regular unprotected sexual intercourse”. Currently, there are an estimated 186 million cases and its increasing prevalence makes it urgent to study its etiology. Thyroid dysfunctions are one of the possible causes of infertility, and this relationship is the object of study of this dissertation. Since thyroid hormones interact directly with receptors present in the reproductive organs and interfere with the hypothalamic-pituitary-gonadal axis, they may lead to menstrual and ovulatory disorders and change the secretion pattern of other hormones important for folliculogenesis, endometrial development and embryo implantation. In men, they compromise spermatogenesis and testosterone synthesis and have effects on gamete motility, ejaculatory capacity and testicular development. Regarding the evidence presented, recommendations have been established as to the approach to be adopted, which include oral levothyroxine supplementation in hypothyroid states, especially if the presence of antithyroid antibodies is detected, and the use of antithyroid drugs, treatment with radioactive iodine or surgery, in hyperthyroid states, being the aim of these interventions to achieve a stable euthyroid state. When this approach is not sufficient to achieve pregnancy, medically assisted procreation techniques such as in vitro fertilization and intracytoplasmic sperm injection may be used. In pregnancy, it is recommended to start levothyroxine treatment or to increase the dose, when thyroid stimulating hormone levels are very high. Conversely, low levels are of no concern and the taking of antithyroid drugs should be avoided. Currently, the establishment of these recommendations and the emergence of new technologies have contributed to boost the fertility of couples and fulfil the desire that many have of becoming parents.
Description
Keywords
Infertilidade Disfunções tiroideias Anticorpos antitiroideus Procriação Medicamente assistida Levotiroxina Fármacos antitiroideus